Printing liquids concentration

Abstract

An example apparatus includes a conveyor. The apparatus also includes a first developer unit. The first developer unit is to concentrate first printing liquid. The first developer unit also is to deliver the first printing liquid to the conveyor. The apparatus also includes a second developer unit. The second developer unit is to concentrate second printing liquid. The second developer also is to deliver the second printing liquid to the conveyor to form a thick layer of printing liquid comprising the first and second printing liquid.

What is claimed is: 
     
       1. A system comprising:
 a conveyor; 
 a first developer unit to:
 concentrate first printing liquid, and 
 deliver the first printing liquid to the conveyor as a first layer of printing liquid; 
 
 a second developer unit to:
 concentrate second printing liquid, and 
 deliver the second printing liquid to the conveyor as a second layer of printing liquid; 
 and 
 
 a wiper in contact with the conveyor, the wiper to remove the first and second layers of printing liquid from the conveyor, 
 wherein the first and second developer units are to receive the first and second printing liquid at a non-volatile solid concentration of no more than 5%, and the wiper is to remove the first and second layers of printing liquid from the conveyor at a non-volatile solid concentration of at least 30%. 
 
     
     
       2. The system of  claim 1 , further comprising a squeegee unit between the first developer unit and the second developer unit, the squeegee unit to apply mechanical and electrical forces to the first layer of printing liquid on the conveyor to concentrate the first layer of printing liquid. 
     
     
       3. The system of  claim 2 , further comprising a plurality of additional squeegee units after the second developer unit, the plurality of additional squeegee units to further concentrate the second layer of printing liquid. 
     
     
       4. The system of  claim 3 , further comprising an actuator to engage and disengage independently each of the squeegee unit and the plurality of additional squeegee units to and from the conveyor to adjust a concentration of the first and second layers of printing liquid removed by the wiper. 
     
     
       5. The system of  claim 1 , further comprising an actuator to engage and disengage independently each of the first and second developer units to and from the conveyor. 
     
     
       6. The system of  claim 1 , wherein the wiper transports the first and second layers of printing liquid to a storage vessel. 
     
     
       7. The system of  claim 1 , wherein the first and second layers mix and become indistinguishable after delivery of the second layer to the conveyor. 
     
     
       8. A method comprising:
 concentrating first printing liquid on a first developer roller; 
 transferring the first printing liquid to a conveyor; 
 further concentrating the first printing liquid on the conveyor using a first squeegee unit; 
 concentrating second printing liquid on a second developer roller; 
 transferring the second printing liquid to the conveyor, wherein the second printing liquid is transferred to on top of the first printing liquid; and 
 further concentrating the second printing liquid on the conveyor using a second squeegee unit, 
 wherein the first printing liquid transferred to the conveyor has a non-volatile solid concentration of at least 15%. 
 
     
     
       9. The method of  claim 8 , further comprising removing the first and second printing liquid from the conveyor, wherein the first and second printing liquid have an overall non-volatile solid concentration of at least 30% when removed from the conveyor. 
     
     
       10. The method of  claim 8 , wherein the first printing liquid further concentrated on the conveyor has a non-volatile solid concentration of at least 20%. 
     
     
       11. The method of  claim 8 , wherein the second printing liquid transferred to the conveyor has a non-volatile solid concentration of at least 20%. 
     
     
       12. An apparatus comprising:
 a conveyor; 
 a first developer unit to:
 concentrate first printing liquid, and 
 deliver the first printing liquid to the conveyor; and 
 
 a second developer unit to:
 concentrate second printing liquid, and 
 deliver the second printing liquid to the conveyor to form a thick layer of printing liquid comprising the first and second printing liquid, 
 wherein the thick layer of printing liquid has a thickness of at least 5 micrometers. 
 
 
     
     
       13. The apparatus of  claim 12 , further comprising a squeegee unit to further concentrate the thick layer of printing liquid, wherein the thick layer of printing liquid has a thickness of at least 5 micrometers after the further concentration. 
     
     
       14. The apparatus of  claim 12 , further comprising a wiper to scrape the thick layer of printing liquid from the conveyor. 
     
     
       15. The apparatus of  claim 14 , wherein the wiper transports the thick layer of printing liquid to a storage vessel. 
     
     
       16. The apparatus of  claim 12 , wherein the first and second developer unit each comprise:
 a developer roller to receive printing liquid; 
 an electrode to concentrate the printing liquid on the developer roller; and 
 a squeegee roller to further concentrate the printing liquid on the developer roller. 
 
     
     
       17. The apparatus of  claim 12 , wherein the first and second developer units are to receive the first and second printing liquid at a non-volatile solid concentration of no more than 5%, and the thick layer of printing liquid is removed from the conveyor at a non-volatile solid concentration of at least 30%.